Please explain raid 5

Discussion in 'Technical' started by tera7, Apr 3, 2009.

  1. tera7

    tera7 New Member

    Ok i need to understand how raid 5 can tolerate loss of one drive.
    I assume that we have a 4 hd(250 gb) raid 5 .we lose the storage capacity of one drive or the storage capacity is 750 *0.75= 562.5.
    If the first is true i really dont understand how.

    That was my thoughts here is the answer:

    Just in case some noob like me thinks that somenthing is missing :rolleyes:
  2. id10t

    id10t Member

    Gee almost 2 months and no answer?

    Here it is...

    Raid 0 - The 0 indicates how much data you can recover when a drive dies. Raid 0 simply bonds multiple disks into one big one, so you have all storage space of all devices. But no failure tolerance.

    Raid 1 - you have a mirror of a drive. 2 physical devices, constant mirror. One drive dies, you can break the mirror and use it solo, or you can remove the bad drive and rebuild the mirror.

    Raid 5 - you have at least 3 drives. Depending on how you are doing the raid you may be able to have one as a hot spare. You get 2/3 of your storage space. Data is written in a way that for each pair of bits, each one is on a different physical device and there is a parity bit on yet a different physical device. Depending on which physical device dies, each triplet will loose one of them - bit 1, bit 2, or parity - but with the other 2 existing, the 3rd can be quickly calculated and replaced onto the replacement drive.

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